im selling my apple powerbook g4 how do i restore it to factory

Drive Partition and Format

1. Boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu.

2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.

3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Apply button and wait until the process has completed.

4. After formatting has completed quit Disk Utility and return to the installer. Install OS X.

Some of the following may apply as well, so read carefully before doing the above.

What to do before selling or giving away your Mac

As you're on a PowerBook G4, you need to use APM and not GUID for the partition scheme.

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I recommend securely erasing the disk using disk utility.

1. Select the disk or partition to erase, then click Erase.
2. Specify a format, then enter a name for the disk.
3. Click Security Options, use the slider to choose how many times to write over the data on the disk, then click OK. — Writing over the data three times meets the U.S. Department of Energy standard for securely erasing magnetic media. Writing over the data seven times meets the U.S. Department of Defense 5220-22-M standard.
4. Click Erase.

Please note, these steps were taken from OSX v10.9 Disk Utility help but they will differ only slightly, You will options to erase the drive once, seven or 35 times. Once is enough. You would need pretty good forensics tools to extract data from a drive erased only once not to mention 7.